boylesg
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You have enough familiarity in this forum to know that without providing accurate information the first thing that will happen here is others demand for details, as the schematic for example.
A scribble done with a little more enthusiasm or less sloppiness would motivate someone to spend a time analyzing your problem instead of trying to decipher hieroglyphics. I`m quite sure you are plenty aware of the standard symbologies adopted for electronic devices.
Hi,
A pencil, a piece of paper and a photo...
A free schematic drawing software
Klaus
In your drawing I see "5V". But I assume thus "5V" is the supply voltage of an electronic device, but not the true voltage at this node.
If so, then this "5V" is useless, or even misleading informatikn.
Klaus
Hi,
In your drawing I see "5V". But I assume thus "5V" is the supply voltage of an electronic device, but not the true voltage at this node.
If so, then this "5V" is useless, or even misleading informatikn.
Klaus
The Arduino is supplied with 5V, this doesn't mean the pin output voltage is 5V, too.5V as in the triac gate is triggered by 5V from an Arduino digital pin.
What's exactly the problem? It should be a standard and easy function for a phone as well as scanner to create and digital picture files.If you knew how slow and painful it is to get photos off my phone or scanner
Is there any better way of protecting the DC circuit from the AC current than what I have done with the 1N4007?
How about using an opto-coupler? Safety first (I am talking about the poor arduino) even if you are using 24AC.
The simplest drawing tool is probably FidoCadJ which is written in Java and runs on most platforms. In my opinion it doesn't come close to the Kicad/Eagle/Protel type of programs for functionality but it is small, free and very easy to use.
Looking at the original problem, I can't see how anything but an isolated connection can be safe here. Even at 24V, if the ground side isn't good it will just push a negative voltage into the Arduino and kill it instantly. I'm not sure the voltage/current capability of the port is sufficient either and even if it was, the triac couldn't possibly fire in all quadrants.
Brian.
What is reliable?Is there no reliable way of protecting the DC part of the circuit from a failed triac?
Hi,
What is reliable?
I recommend to read through the datasheets and keep within their specifications, then it should be reliable.
If you don´t need isolation, then I see no reasn why you should use optocouplers.
My recommendation: Don´t protect your DC part from failing triac, but protect the triac from fail.
*****
Your circuit with diode for protection:
It only can protect against one error: the gate goes high positive voltage caused by a damaged triac... Then the diode will protect the driving circuit.
But when the gate goes high positive voltage, then I expect it to go high negative voltage, too...now the diode doesn´t protect anymore.
****
From your description we can not know whether a relay or a triac is suitable.
Btw: What if the relay fails?
Klaus
Connecting the two circuits together (AC and DC) is not impossible but you have to be extremely careful with current paths and consider what happens if for example the AC is present but the DC fails. The diode will offer no protection, it would just act as a negative voltage rectifier and feed the DC to the Arduino pin in the wrong polarity.
By FAR the best solution here is to use an opto-isolator such as a MOC304x to fire the triac. It gives excellent voltage isolation, can be driven directly from the Arduino (via a single resistor to limit LED current) and it will let the triac conduct over the whole AC cycle instead of only half of it. They are very reliable, small, inexpensive and cost less than a relay!
Brian.
"sufficiently isolated": We don´t know which relay you use, thus we don´t know if it is sufficiently isolated.And as far as I am aware, the DC coil and the AC contacts are sufficiently isolated for there to be no consequences if the AC contacts short circuit or something.
Am I wrong about that assumption?
Why does an electronic part fail:What is your suggestion for protecting the triac from fail? Fuse perhaps?
What is your opinion of these optocoupled triacs Brian?
If you have lots of triacs already in pocket, you can just get a set of general purpose optocouplers. And they can be used in other places too. Because you are trying these circuits, it is good to be careful.
I'll put it down to inexperience with triacs - bought them before I understood fully how to use them.
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